Process chambers used for deposition in display and semiconductor industries are typically periodically cleaned, depending on the product, to remove contaminants and residue deposits from the walls and the gas distribution plate by dry cleaning using plasma enhanced etching. Some traditional solutions use a fixed clean endpoint time for the cleaning process. Fixed times may lead to under-etching and/or over-etching, which can cause damage to the chamber. Under-etching can create particle issues while over-etching can cause accelerated hardware wear by halogens and especially fluorine.
Generally, a chemical vapor deposition (CVD) chamber clean process is closely monitored for potential damage caused by underetch and overetch. However, continuous monitoring of the cleaning process run-after-run on multiple chambers can be costly. There have been numerous previous attempts that use optical emission or detection spectroscopy to estimate the clean endpoint time. Traditional solutions monitor the intensity of the reflection of a light beam or the variations of optical wavelengths emitted from the plasma as the plasma undergoes gas phase changes. The signal to noise ratio is not sufficiently high in many cases. Furthermore, the associated hardware to measure the amplitudes of such signals are expensive since the signal varies substantially from element to element.
Some traditional solutions attempt to estimate the clean endpoint time using pressure. A stabilized pressure may serve as an indicator that the cleaning process can be ended. However, conventional pressure based solutions usually result in endpoints that are noisy and exhibit large time fluctuations due to the nature of the pressure measurements. Traditional solutions generally use a small data set to determine when pressure stabilizes as an indicator that a clean endpoint time has been reached. For example, some conventional solutions may use only a few seconds to determine if pressure has stabilized. Small windows of time may include noise which typically leads to inaccurate clean endpoint time calculations, and may thus be generally unreliable.